The little transmission mount on my 1970 240Z has finally died. The rubber insert has deteriorated and separated, so I bought a new replacement unit from MSA. It actually appears beefier than the original stock item and should last a long time. This will eliminate the annoying "CLUNK" between each shift.

MY PROBLEM IS: Altho the bolts for this mount are easily accessible from under the car, the nuts which secure them AREN'T. Those are captured (and totally inaccessible) inside a sheetmetal box, which is formed by several sheets of body and frame metal. Trying to loosen the bolts from below is a futile effort, since the nuts loosen just enough to let the bolts spin freely but then won't allow them to back all the way out.

Vinny says the best way to access the nuts is to drill a hole (hole saw) into each side of the transmission tunnel from inside the car, drop a socket and extension down onto the nuts, and hold them that way. We would fill the holes with a solid rubber grommet when we're done, so we don't have to cut into the car if we ever have to do this again.
After looking the whole thing over, I think he's right.

But before any cutting happens to my dear old car, I want to check if anyone else has ever approached this problem from any other angle.

Is there any better way to access those captured nuts on top of the transmission mount bolts?

And WHAT was Datsun thinking when they built a whole car around two nuts, making them completely inaccessible???

Frank

The two nuts that Datsun designed the car around were you and me!
Remember, we have been around virtually since the Z'S beginning.
Although I would relinquish my position as one of the two nuts to Mr.
Sharp if you would relinquish yours to Mr. Taddonio, who has claim to
the title already!

_________________
All Z Best,.......Kathy & Rick

1969 Z.CAR (#00013 10/69) 8/30/76
1969 ITSA.Z (#00171 11/69) 8/24/73
1970 OLD.Z (#06289 6/70) original owner
1971 510 2dr since 12/31/75
1969 1600 rdstr (our 160-Z)
1971 (#19851 1/71) sold
1975 75.Z (#01343 1/75)

They WEREN'T thinking, which is exactly why they redesigned how the transmission mount bolts to the body beginning with the series two cars and continuing through 1978!

The later mount has the attachment bolts running horizontal through the mount instead of vertical up into the capture assembly.

If it was me, I would remove the early mounts and weld some later mounts onto the chassis. If you don't want to go to that degree of surgery, I would try Vinny's approach, although I would be concerned that it would compromise the strength of the mount itself.

In any event, the old has to come off! Good luck Frank....

_________________
John Taddonio
1970 240Z
1977 530Z
1984 300ZXT
zcarnut@hotmail.com
FB: Zccr zcarclubofrochester

A title I proudly claim! LOL! I also posted proudly on my 350Z!

_________________
John Taddonio
1970 240Z
1977 530Z
1984 300ZXT
zcarnut@hotmail.com
FB: Zccr zcarclubofrochester

You guys slay me!

The holes will be as small as possible ~ just enough to allow an extension to drop in there with a socket on it, to hold the nuts. Maybe we'll weld them back up, but I think two rubber dooliez will serve to fill the holes OK afterward, like the rubber plugs which fill the drain holes in the floorboards.

I can't picture how two small holes would affect the integrity of the mount, since the mount is outside (under the transmission) and the holes will be inside, in the transmission tunnel walls. But if it appears to be an issue, we'll just weld 'em back up instead.

Rick, I can't relinquish my position any more than you can! The same bug bit you and me, as well as Ross, and John, and Paul, and Bryan, and Mike, and about 300 other members of this Club. It's been called an Affliction, an Obsession, a Compulsion, an Addiction, and 'The DeZees'. There's no known cure, and if there was, I wouldn't take any of it anyway. I agree to be a Z nut for life.

Thanks guyz ~ appreciate the advice.

Frank

Frank, I can't picture the area you are working on because I think both of my cars have the newer design. However, is there anyway to drill a tiny hole about 1/8 - 1/4" and drop some JB Weld onto the nut inside the chamber? If you could get the JB Weld in the right spot, along the edges of the nut, you might be able to get the bolts out nicely with minimal invasive surgery. Orthroscopic, if you will.

_________________
-Dave
76Z Turbo'd
72 In Progress---DONE!

Sounds like a good idea, but I would still have to have access to "the box" to replace new nuts onto the replacement bolts.

This 'box' is formed by several folds of floor and transmission tunnel sheet metal welded onto heavier 'frame' supports (not actually frame rails). It's entirely enclosed and even dropping the transmission would not give access to it. The nuts (and probably washers) are completely captured in a small steel (well, 'Datsun metal') chamber. The two chambers are formed along the sides of the transmission tunnel, just a few inches forward of and very near the forward seat rail on either side of the transmission.

A small hole saw should give us access to the tops of the nuts. I really do want to be as 'orthoscopic' as possible tho ~ just large enough to let a short extension or swivel socket in there to hold the nut from above, while the vertical bolt gets turned out from below the car. If I place the hole just right, I might even be able to fix a straight box wrench onto the nut for both operations.

It's frustrating to think that the engineers never envisioned this operation being done ~ as if they never expected the transmission mount to fail, or else they never envisioned the car lasting long enough to require this replacement.

A picture is worth a thousand words, so I should Post some up here if I can get some good shots of it all. Sounds pretty confusing when I try to describe it. Just one more unique feature of the 1970 Z car!

Frank

Ahhhh, the hidden nut in the body senerio. The first thing I do is get something in between the now loose mount and either pry it or press it enough so the nuts won't turn but the bolt will. Soaked in PB blaster would help. Or hit the spot underneath with the welder and it will burn through to secure the nut. Been there done that. Cutting through the body, ummmm last case senerio, but not necassary. Even though they changed the style, to me IMO, It looks like the older style was more rigid.

We tried pressing down on the mount with several lever bars, but none of them held the nut tight enough. I like the JB weld idea, but if it splashed into the thread area in the center of the nut, it might effectively weld the nut to the bolt. Also, I would not be able to replace the old nuts with new ones, since the old ones would then be 'welded' to the bottom of the box.

Datsun could have prevented this by originally spot-welding the nuts to the bottom of the box before they sealed everything up. I think it was just an oversight on their part, so every '69-'70 car probably has this problem. I can't be the first guy who ever faced this problem.

We even discussed cutting the bolt off from below, but that would have been a disaster ~ it would have left the top half of the vertical bolt attached to the nut, with no possible way of removing it all from the 'box'.

I wish we could get Danny Linquist to chime in here ~ he used to work on these and maybe he has replaced a few of them.

Hey Frank, Vinnnie had done mine on my 240z call and ask him how he went about it.. Good Luck.. Scotty.

Makes me thankful that mine came out with no problems!!

And no, how could Datsun have expected their $3500 car to still be around 40 years later! If you have ever taken apart a series one car down to the shell, it is apparent where costs were shaved in the construction process. Not cheaply built, but rather cheaply DONE. That's how they brought it in at the $3500 price point.

_________________
John Taddonio
1970 240Z
1977 530Z
1984 300ZXT
zcarnut@hotmail.com
FB: Zccr zcarclubofrochester

Frank, Vinny has the correct approach. It's quick and easy, plus you won't drive yourself crazy.

Good luck.

Danny

Frank, I do not believe changing to that new mount from MSA will get rid of the clunk at all. The clunk you get in the rear end is from the angle off the diff to tranny. This is why the later Z cars got the back diff position.

r/t mount pic:


Series 1 install:
http://forums.hybridz.org/showthread.ph ... =ron+tyler

Order here:
http://forums.hybridz.org/showthread.ph ... =ron+tyler

As far as a series one question, you can ask Joe (rags). He installed the mount above in his series one car.

_________________
Clive Bogle President - New York Z Car Club - NYZCC.COM
1971 240Z - LS1/T56
1974 260Z-L30
1976 Fairlady Z

I too endorse that front differential mount. More go, less clunk, no harshness, no surgery to the chassis required.

If that nut is really rusted onto the end of the bolt, you will have to gain good access to it and Vin's way is the ultimate solution. Don't think of it as cutting up your car, think of it as fixing Nissan's mistake.

_________________
-Dave
76Z Turbo'd
72 In Progress---DONE!

Hahahaha ~ I like that.

Vinny drilled a small hole and grabbed the nut as described. The mount came right off and the new one from MSA is nearly twice as beefy as the original one was. My entire transmission now feels far crisper and tighter, and unless I really bang-shift it, the CLUNK is gone. Problem solved.

Thanks to all who took time to contribute to this Thread, and Clive, I might want to speak with you about those braces soon.